Device for preventing short circuiting flow around impellers



jam. 5, 1932. A. R. was 1,839,514

DEVICE FOR PREVENTING SHORT GIRCUITING FLOWAROUND IMPELLERS Filed Jan.23, 1929 1N VE/w-oe: [4277102 8. A E/s,

illustrated a preferred embodiment of my invention, 7

Fig. 1 is a utility view, partially in section, illustrating one type ofpump in which my invention is particularly applicable.

Fig. 2 is a cross-sectional view illustrating the details of myinvention.

Fig. 3 is a sectionalview taken on the line 3-3 of Fig. 2. a a

Fig. 4 is a graph on which a curve of pressure against output isplotted.

Referring particularly to Fig. 1, Ifhave illustrated a deep-well turbinepump comprising a pump section 10, positioned in the lower end of a well11, and inside a well casing 12. The pump section is supported by asuitable discharge tube 13 which extends upward to the surface of theground and is connected to a pump head 14. A shaft 15 extends from thepump section 10 upward inside the discharge tube and is rotated by ameans 16. The pump section 10 is formed The details of these pump bowlsmay best be understood by reference to Fig. 2 wherein two of the pumpbowls 19 are illustrated as being connected together by bolts 20 passingthrough an upper flange 21 of the lower bowl and being threadedlyreceived into the lower walls of the pump bowl thereabove. An impellerchamber 22 is formed in each of the pump bowls, a lower portion of thisimpeller chamber being defined by an upper wall 23 of the pump bowl 19immediately therebelow. Each of the impeller chambers 22 communicatesbetween an intake passage 24 and a dis charge passage 25, these passagesbeing formed in a pump bowl structure 26 which comprises the differentpump bowls 19.

Positioned in each impeller chamber 22 is an impeller 30 having'a hub 31which is secured to the shaft 15 by any suitable means such as a key 32.The lower portion or eye 33 of the impeller extends into a bore 34 in amanner to leave a primary clearance space 35 therebetween, thisclearance space being ordinarily small.

Formed through the impeller is an impeller passage 36 which has vanes 37therein. The

passage 36 has an inlet-port 38 in communication with the intake passage34 and has an outlet port 39 in communication with'the dischargepassage25. V

. When the shaft 15 is rotated, each of the impellers draws well fluidupward through the adjacent intake passage and discharges this fluidinto the adjacent discharge passage 25. This particulartype ofcentrifugal impeller has the property of centrifugal- 1y dischargingthewell fluid from the outlet port '39 at a relatively high total head.

At the point of discharge from the impeller, this total head is dividedinto a high velocity head and a rather low pressure head. As soon asthis fluid reaches the discharge passage 25 the pressure head becomeshigh and the velocity head lowers a corresponding amount. Thus, thepressure in the discharge passage 25 invariably higher than the pressurein the intake passage 24, and this differential pressure has heretoforeinvariably set up a short-circuiting flow around the lower shroud 42 ofthe impeller 30 in a direction indicated by the dotted arrow 43. Thisflow takes place through an auxiliary chamber 44 formed between thelower shroud 42 and the upper wall 23. Due to the fact that the velocityhead of the fluid changes into a high pressure head ver soon afterenterin the dischar e oas- J7 a .z: 1

sage 25, any abrasive particles which are carventional type of pump areallowed to drop into the chamber 44. Heretofore great difficulty hasbeen encountered due to these abrasive particles collecting in thechamber 44 and wearing the upper wall 23, and especially the lowershroud 42 of the impeller.

Various types of labyrinth packing have been devised for decreasing thisshort-circuitingflow, but it has been impossible to eliminate thisshort-circuiting flow. F urthermore, these packings are invariablyplaced adjacent the eye of the impeller, thus allowing an accumulationof sand below this impeller even though the short-circuiting flow isdecreased. 7

My invention comprises the formation of a skirt 47 on the outer portionof the lower shroud 42, this skirt extending in close proximity to acylindrical wall 48 of the impeller chamber 22. A secondary clearancespace 49 is formed therebetween, this clearance space ordinarily beingin the neighborhood of several thousandths of an inch. Formed throughthe skirt 47 are one or more upwardly inclined openings 50. As bestshown in Fig. 2, the inner ends of these openings communicate with theauxiliary chamber 44, while the outer ends of these,- openingscommunicate with the clearance space 49. The openings 50 act as anauxiliary pumping means tendstage, and as abscissa the output ingallons.

A typical test curve has been plotted, this curve having a decided droopindicating that as the output of the impeller is increased,

the total head developed by this impeller decreases. In fact, with theparticular impeller tested in securing the information disclosed in Fig.4, the total head per stage un der no output was feet. As the output ofthe impeller increases, or, in other words, as more fluid passed throughthe passage 36 thereof, the total headperfstage dropped.

When the output was900 gallons per minute, the total head was in theneighborhood of 36 feet instead of 60 feet as pre'viously. if

ft is well established that the total-head developed by an impeller is afunction of, and

nearly proportional to, the maximum radius 1 I below the mouth of theopenings 50 extends of the passage 36 therein. In O 'tl16IWOI'ClS, witha given output, the total head developed by an impeller is proportionaltothe distance between the center of rotation of the shaft and the mouthof the outlet port 39. I

In Fig. 2 l have illustrated an impeller,

' the mouth of the outlet port 39' of which is not parallel to the axisof rotation, but instead converges upward,'so thatthe upper portion 52of this mouth is closer to the axis of the shaft 15 than isthe lowerportion 53 of this mouth. With this particular type of.

impeller, the total head developed thereby with a given output issubstantially proportional to the mean distance between the axis ofrotation of the shaft and the portions 52 "and. 53 of the mouth of theoutlet port 39.

The outer periphery of theskirt 44 is positioned at a radius which isgreater thanthis mean difference, and it therefore follows that thepressure developed by the centrifugal.

force of the fluid in the openings is always greater than the pressuredeveloped in the.

passage 36 of the impeller, even though the flow through this passage 36is reduced to,

substantially zero. In other words,the impeller 30 at zero output mightdevelop a head I of 60 feet in the passage 86, but the head developed inthe openings 50 would exceed this value by several feet due to the factthat the mouths of these openings are at a greater radial distancefromthe shaft than the mean distance between the shaft and'the portions52 and 5". This causes a flow of iiuid upward through the clearancespace 35 and into the chamber 4%, this fluid beingdischarged through theopenings 50 and into the clearance space 49.

It should be understood that the volume of fluid passing through theopenings 50 is at all times very small due to the proximity of thecylindrical wall 48 to the mouthsof the openings 50, and that thereforethe total head developed by the openings 50 is not materiallydecreased'by a large output therethrough. In other Words, the pumpingmeans formed by the openings 50 wouldfollow a curve 59 shown in Fig.4,this curve lying above the curve and extending only a very shortdistance along the abscissa scale.

Whenthe output of the impeller increases,

the total head developed thereby also decreases, thus accentuating thediiference'in values ofhead developed by the passage 36 and the openings50.

To insure that the flow of fluid passing through the openings 50 b edirected upward into the discharge passage 25 rather than the clearancespace 35. ,VGlOCltY which exists between the streams of beingshort-circuited around the lower edge of the skirt 47, I inclinetheseopenings up- {ward, as best indicated in Fig. 2. Furthermore, themouth of each'opening 50 is only a small distance below a ledge 60defining the upper end of the cylindrical wall 48, while the portion ofthe periphery of the skirt 47 a material distance downward in close"proximity to the cylindrical wall 48.

The clearance space 49 in effect actsas a sealing means, due to the verysmall width of this space, this sealing means being ordinarily filledwith a fluid. The sealing area larger, however, than that above themouth of the openings 50, inasmuch as these openings are positioned asheretofore described. There 19 thus'very little resistance to flowupwardthrough the clearance space l9 from;

around the lower edge of the skirt M.

It should thus be apparentthat any fluid entering the auxiliary chambera l will be dis charged through the openings 50 lrrespective of theamount of flow through tl e passages 36-of the impeller. it shouldfurther be ag-J parent that in my invention the directionof flowthroughthe chamber is'reversed from,

the ordinary direction of flow. In other words, the pumping means, drawsthe fluid through this chamberin a direction indicated by the arrow .62.

Furthermore, by makingv the clearance space el9 extremely narrow, thisclearance vspace restricts the flow of fluidthrough the chamber 44: thusinsurin a low velocit in a o m ihe dlh'erential fluid passing throughthe intake passage 2i and the clearance space 35 1S usually greater thanten feet per second. In f'act,the velocity of the fluid in the clearancespace 35 is so low that abrasiverparticles will not be raised thereby,but will gravitate therefrom and into thelarger and faster fluid streampassing through the intake passage 24-. This action'is important to'thisinvention and pr vents any mate wear between the skirt r? and thecylindrical wall 48. It is thus im possible for any abrasive particlesto accumulate between the upper wall 23 and the lower shroud of theimpeller and the wear which heretofore took place due to thisaccumulation of abrasive particles is ent'rely eliminated. I

The simplicity of the means for accomplishing these desirable resultsshould be apparent. No additional working parts over those ordinarilyused are needed in building this type below the mouth of the openings50is much :3

aids in preventing a'short-circuiting flow more machine work is requiredon the pump j let port therein; a pump bowl structure in' which saidimpeller rotates, there being an auxiliary chamber between said impellerand said pump bowl structure, said structure providing an intake passageand a discharge passage communicating respectively with said inlet andoutlet ports; and an auxiliary pump means for drawing fluid intosaidauxiliary chamber from said intake passage and discharging it into saiddischarge passage.

2. In a turbine pump, the combination of: a pump bowl structureproviding an impeller chamber; an impeller having upper and lowershrouds and being adapted to rotate in said impeller chamber; and meansfor setting up between said lower shroud and said pump bowl structure aflow of well fluid which parallels the flow of said well fluid throughsaid impeller.

3. In a turbine pump, the combination of an impeller having an inletport and an outlet port therein; a pump bowl structure in which saidimpeller rotates, there being an auxiliary chamber between said impellerand said pump bowl structure, said structure providing an intake passageand a dischargepassage communicating respectively with said inlet andoutlet ports; and a skirt on said impeller and having an opening.therein actmg to centrifugally discharge fluid from' said auxiliarychamber into said discharge passage.

'4. In a turbine pump, the combination of an impeller having an inletport and an outlet port therein; a pump. bowl structure in which saidimpeller rotates, there being an .45

auxiliary chamber between said impeller and said pump bowlstructure,said structure providing an intakepassage and a discharge passagecommunicating respectively with said inlet and outlet ports; anauxiliary pump means for drawing fluid into said auxiliary chamber fromsaid intake passage'and-discharging it into said discharge passage; andmeans for restricting the flow of fluid pumped by said auxiliary pumpmeans so that-the pressure developed thereby is always greater than thepressure set up in said outlet port of said impeller.

5. In a turbine pump, the combination of: an impeller having an inletport and an outlet port therein; a pump bowl "structure in which saidimpeller rotates, there being an auxiliary chamber between said impellerand said pump bowl structure, said structure providing an intake passageand a discharge passage communicating respectively with said-inlet andoutlet ports; a skirt on said impeller. and having an opening thereinacting to centrifugally discharge fluid from said auxiliary chamber intosaid discharge passage; and means for maintaining the flow of fluidthrough said opening substantially constant. p V

6. In a turbine pump, the combination of: a pump bowl structure definingan impeller chamber bounded on one side by a cylindrical wall; animpeller adapted to rotate in said impeller chamber; askirt on saidimpeller rotating in close proximity to but spaced from said wall; andan opening through said skirt and adapted to centrifugally dischargefluid between said skirt and said cylindrical wall.

"7. In a turbine pump, the combination of: a pump bowl structuredefining an impeller chamber bounded on one side by a cylindrical wall;an impeller adapted to rotate in said impeller chamber; a skirt on saidimpeller rotating in close proximityto said wall; an opening throughsaid skirt and adapted to centrifugally discharge fluid between saidskirt and said cylindrical wall; and a settling space through which saidfluid must pass beforereaching said opening.

8. A combination as defined in claim 6 in which'said impeller hasanooutlet port discharging into a discharge passage of said pump bowlstructure and in which said opening is inclined in a manner to forcesaid fluid into said discharge passage.

9. In aturbine pump, the combination of: a pump bowl structure providingan impeller chamber, a portion of which is defined by a bore in saidstructure and a cylindrical wall concentric with said bore; an impelleradapted to rotate in said chamber, said impeller having an eye extendinginto said bore in a manner to form a primary clearance spacetherebetween communicating with an intake passage and with an auxiliarychamber formed between said impeller and said pump bowl structure; and askirt formed on the periphery of said impeller and rotating adjacentsaid cylindrical wall in a manner to form asec'ondaryclearance spacetherebetween communicating with said auxiliary chamber and with adischarge passage, said skirt providing an opening therethroughcommunicating with said auxiliary chamber and said secondary clearancespace.

10. A combination as defined in claim 9 in which the mouth of saidopening opens on said secondary clearance space at a point near that endof said secondary clearance space which communicates with said dis- 1end of said secondary clearance space which communicates with saiddischarge passage.

12. A combination as defined in claim 9 in which said primary clearancespace is substantially vertical and in which said secondary clearancespace limits the velocity of said fluid in said primary clearance spaceso that abrasive particles carried by said fluid may settle therefrombefore the fluid enters said auxiliary chamber.

13. In a turbine pump, the combination of: walls defining an impellerchamber communicating with an intake and a discharge passage; animpeller rotating in said impeller chamber to pump a fluid containingabrasive particles from said intake passage through said dischargepassage, said impeller providing an eye rotating in close proximity tosaid walls to define an upright clearance space, said fluid movingthrough said eye and having a velocity adjacent the mouth of saidclearance space to carry said abrasive particles upward therewith; andmeans for setting up an upward flow of said fluid through said clearencespace of insuflicient velocity to raise said abrasive particlestherewith. V

In testimony whereof, I have hereunto set my hand at Los Angeles,California, this 18th day of January, 1929.

ARTHUR R. VVEIS.

